Electronically commutated motors (ECMs) are driven via controlled application of drive currents to stator coils to controllably rotate a rotor. In many ECMs, the rotor includes one or more permanent magnets that interact with the magnetic field generated via the stator coils. In many ECMs, the drive currents applied to the stator coils are generated via a switching assembly that is controlled via a control unit to controllably connect and disconnect the stator coils to a DC voltage and an electrical ground.
The control unit controls the switching assembly based at least in part on a rotor orientation estimate. The rotor orientation estimate is used to ensure that the switching assembly is controlled so that the stator coils produce magnetic fields suitable to produce a desired torque on the rotor. Many different approaches for estimating rotor orientation exist.